1. Field of the Invention
This invention provides a method for testing the containment spray system of a nuclear reactor.
2. Description of the Prior Art
Among the auxiliary systems comprising the safeguard systems of a nuclear reactor facility is a containment spray system. In the event of an accident causing reactor coolant to flow out of the primary reactor system, the containment spray system will operate to deluge the primary components with a mixture of water and a neutron absorber. The containment spray system typically comprises a large amount of spray conduits containing spray nozzles, located in the upper portion of the containment structure. Safety requirements dictate that this system must be tested prior to initial plant operation as well as at periodic intervals during the plant life.
To date no system exists which accurately and simply can be used to perform the necessary testing. Further, none of the prior art systems contain means for actual physical recording of the test. Presently used techniques are based upon the principle that the testing of the containment spray system is satisfactory if air flow or smoke through the spray nozzles indicates that the nozzles are not plugged. Prior art designs, therefore, fall into two categories. The first consists of a smoke test wherein smoke is injected into the system and is observed to flow out of the spray nozzles. The second system comprises using a helium filled balloon suspended at the nozzles whereby the motion of the balloon is observed when air flow is introduced into the spray system. Each of these prior art methods has significant drawbacks.
The main problem with the smoke test is that smoke injected into the spray system quickly fills the containment atmosphere with the smoke thereby obscuring the nozzles. Secondly, particulates are added to the containment atmosphere, by the smoke, which causes an undesirable loading of the containment filtration systems. These factors therefore require that the smoke test be run in intervals, which is both time consuming and costly. A small number of nozzles are observed during an interval, and the test is then stopped to clear the containment of smoke before testing is restarted. The balloon test is also costly in terms of time requirements and at best gives a relatively crude test of the operability of the spray system. This test is performed either from the operating deck, which is typically greater than a hundred feet below the elevation of the spray system, or from scaffolding erected at that high elevation. If performed from the operating deck, control and observation of any movement of the balloon is very difficult. If performed from scaffolding, the test is expensive in terms of erection time, as well as a high risk factor for personnel who must operate on the scaffolding. The balloon test is also very susceptible to air currents within the containment. Personnel controlling the balloon at the operating deck level are also susceptible to radiation exposure. Prior balloon tests required two to three days for completion, and could not be performed concurrently with the refueling operation, as the testing personnel may interfere with refueling personnel. A smoke test requires at least as much time as the balloon test.
The time and safety problems associated with prior testing systems are eliminated by this invention. Further, the invention provides means for accurate recording of the test.